On 6/4/2013 7:20 AM, Arfa Daily wrote:


That is 100% correct, and an adept description of how such errors are
barely noticeable on a black and white picture. Understand also that
we are talking pure CRT physics here. Don't get confused by colour
signal weightings that are part of the encoding and transmission
process. Whilst there are some differences in the efficiencies of the
phosphors, and the eye is non linear in its response to the visible
spectrum, those differences are not huge, and for white through shades
of grey, the three beam currents will not be wildly different for a
CRT that's in good emmissive order. Hence the reason that mass beam
landing errors are not anything like as important to the reproduction
of an accurate grey, as you might imagine. The fact that such errors
are much easier to see on a colour picture may well be a perceptual
one, as the human eye / brain combination, is extremely good at
handling colour perception. Single beam landing errors - convergence
errors - are of course, much easier to see on a black and white picture.

I agree with all of the above. The only other possible extra point I
could add is that purity adjustments are nominally made with a solid
raster, and typical gamma for consumer color TV may cause compression /
squashing / clipping of the video drives, making the impact of relative
phosphor efficiency differences all the less noticeable.

As to questioning the credentials of the people that have replied to
this, being new, you should probably be aware that the William has a
lifetime's experience at the sharp end of service, sales and technical
writing, Bob has lectured the stuff, I spent many thousands of hours
of my life working on this stuff at nuts and bolts level, and Phil,
for all his occasional rants and outbursts, is a highly qualified
service engineer whose technical understanding and ability is without
question.

I have no issue with the matter of whether such effects are, as you and
others have stated, correctly described, and conceded this a day or two ago.

Being a design engineer, an inveterate tinkerer, and one who very much
needs / wants to understand the underlying "why and how does it work?",
my challenge has really attempted to gain this critical thinking and
point of view. I previously thanked others for offering such insight and
do so again here and now, with an apology, if I have somehow failed to
make this apparent. The insights and explanations of those who clearly
know better than I do is much appreciated.